Signature batches are typically formed by moving a bucket into a signature stream to intercept and collect signatures thereon until a batch of the desired number of signatures have been collected, at which time another bucket is moved into the signature stream and begins the signature collection anew.
The batch of signatures collected upon each bucket is delivered to a turntable. Since the thickness of the signature is greater along its folded edge, it is typical to form compensated stacks of signatures each comprised of a plurality of signature groups called batches, with the folded edges of the signatures in each batch displaced by 180.degree. relative to the folded edges of the signatures in the adjacent batch, to compensate for the uneven stack height otherwise encountered in uncompensated stacks.
A compensated stack is formed by delivering one or more batches, each having a predetermined count of signatures, to the stacker turntable. After delivery of the first batch and prior to the delivery of the next batch, the turntable is rotated through an angle of 180.degree. in readiness for receipt of the next batch. This operation continues until the desired number of batches have been delivered to the turntable, at which time a pusher rod is activated to remove the completed compensated stack from the turntable and to deliver the stack to a cooperating conveyor for subsequent handling. The turntable need not be rotated after the compensated stack is removed from the turntable.
The signature stream typically enters into the signature stacker with the signatures arranged in overlapping fashion, folded edges forward. A sensor of either mechanical or optical type senses incoming signatures typically by detection of the folded edge. A count signal developed by the sensor is applied to a counter, which counts the signatures sensed by the sensor.
Each one of a plurality of chain driven buckets is selectively consecutively latched in the "home" position in readiness for an intercept operation. The bucket is typically sprint-mounted to the chains and the spring is charged when the bucket is latched in the "home" position. On reaching a predetermined count, the bucket latched in the "home" position is unlatched whereupon the forces of the charged springs rapidly urge the tines of the bucket into the signature stream, causing signatures to be collected upon the bucket released from the "home" position.
As signatures are collected on the bucket, the bucket moves downwardly and ultimately drops out from beneath the completed batch of signatures allowing the batch of signatures to fall upon the turntable.
A pair of upright side walls extend from opposite sides of the rotatable turntable to aid in the formation of a neat stack.
When the compensated stack comprised of one or more individual batches is completed, the stack is removed from the turntable of one conventional apparatus by one of two pusher rods arranged at opposite ends of a chain drive arranged beneath the stacker platform. The stacker platform is comprised of two platform halves spaced apart by a clearance gap through which the pusher bar moves to discharge the compensated stack from the turntable and on to a cooperating conveyor. The push rod and push rod drive assembly rotate in unison with the stacker turntable requiring large forces for both accelerating and decelerating the turntable and push rod assemblies and their rotation and discharge mechanisms.